With wanted posters off to the side, James L. Turgal, Jr., right, FBI Special Agent in Charge, listens as Laura E. Duffy, United States Attorney Southern District of California, announced the indictments on five suspects involved in the death of U.S. Border Patrol agent Brian Terry.AP

TUCSON, Ariz. — Authorities made a rare disclosure Monday linked to the botched gun-smuggling investigation known as Operation Fast and Furious, revealing the identities of four men accused of involvement in the shooting death of a U.S. Border Patrol agent 18 months ago.

The announcement comes in the wake of pressure from U.S. House Republicans who led a vote to hold Attorney General Eric Holder in contempt of Congress, criticizing the nation’s top prosecutor for withholding information related to the probe.

Operation Fast and Furious was launched in 2009 to catch trafficking kingpins, but federal agents lost track of many weapons they were trying to trace.

Since the fatal shootout near the U.S.-Mexico line in December 2010 revealed deep flaws in the government’s weapons trafficking case, federal authorities have repeatedly declined to reveal material related to the death of Border Patrol Agent Brian Terry, such as what became of the gun used to kill him.

Critics have hammered federal authorities for allowing informants to walk away from gun shops with weapons, rather than immediately arresting suspects and seizing firearms.

Operation Fast and Furious focused on an accused smuggling ring suspected of purchasing guns for the brutal Sinaloa cartel. Some of the weapons acquired illegally with the government’s knowledge were later found at crime scenes in Mexico and the U.S.

U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives agents eventually lost track of about 1,400 of the more than 2,000 weapons — including AK-47s and other high-powered assault rifles — that authorities believed were headed for Mexican drug cartels.

Smuggling operations often seek out firearms in the U.S. because they have limited access to weapons in Mexico, due in part to very restrictive laws there.

Border bandits have operated in the region for decades, running weapons and drugs and robbing and sexually assaulting illegal immigrants.

The release of the suspects’ identities Monday came with the offer of a $1 million reward for information leading to their capture.

It marked the first time all five people accused of being involved in the shooting were named by authorities.

Authorities had released Manuel Osorio-Arellanes’ name last year. He has been in custody since his arrest on the night of the shooting.

The disclosures are among few released by authorities despite repeated requests from congressional leaders and news organizations, including The Associated Press. The FBI, ATF, and U.S. Customs and Border Protection have all denied Freedom of Information Act requests that seek reports and other documents in the investigation of the shooting.

The information regarding Terry’s death is the first update in the case since the contempt vote against Holder in June.

The previous disclosure in the case came when a straw buyer who purchased two rifles found at the shootout scene pleaded guilty to firearms charges in April. Jaime Avila faces up to 10 years in prison when he is sentenced in September.

So far, 11 people in what the government says was a 20-member smuggling ring have pleaded guilty to various charges.

It remains unclear whether the bullet that killed Terry came from the Fast and Furious investigation.

Manuel Osorio-Arellanes faces murder charges in Terry’s death.

He has pleaded not guilty. Manuel Osorio-Arellanes was shot during the gunfight and later told investigators that he had raised his firearm toward the agents but didn’t fire at them, the FBI said in records.

Much of the information in Manuel Osorio-Arellanes’ case has been kept from public view after a judge sealed records in spring 2011.

Six news organizations, including The AP, asked for the records to be unsealed, and earlier this year prosecutors agreed to make the information public.

However, the records released have disclosed little about the circumstances of Terry’s death.

Another man, Rito Osorio-Arellanes, was in custody prior to the shootout and has pleaded not guilty to a lesser charge in the case.

Terry, a former Marine and Michigan police officer, was part of an elite squad similar to a police SWAT team that was sent to the remote areas north of Nogales known for border crime, drug smuggling and violence.